1. Field of the Invention
This invention relates to an apparatus for applying surgical fasteners to body tissue and for severing body tissue with a knife, and more particularly to an improved knife having a non-linear cutting edge for severing tissue when the cutting edge engages body tissue.
2. Description of the Related Art
In recent years, endoscopic, laparoscopic, and arthroscopic surgical procedures have become increasingly common. Endoscopic, laparoscopic, and arthroscopic procedures require the surgeon to cut organs, tissues and vessels far removed from an;entry point into the body. In such procedures, the time and space to perform surgery is critical. Performing the procedure with the least number of devices possible reduces the risk of surgeon error, infection, and other potential complications associated with subsequent reintroduction of instrumentation into the body. As a result, multipurpose instruments capable of severing and adjoining tissue were developed to perform both functions during a single placement within a body.
In these surgical operations it is often necessary to adjoin two hollow body organs along side each other, with their longitudinal axes positioned generally parallel to each other, and to effect a longitudinal cut through the contacting circumferential walls of the two organs in order to open them to each other. After joining the two organs, they essentially constitute a single hollow chamber along the length of the cut. Correspondingly, the circumferential portions of the two adjoining organs on each lateral side of the cut must be sutured by at least one line of "stitches" in order to maintain the integrity of the union.
Instruments capable of performing both the severing and adjoining of tissue are known in the art, and are described in U.S. Pat. Nos. 3,079,606, 3,490,675 and 3,499,591. Such multipurpose instruments are generally referred to as linear cutting staplers and typically include two elongated fingers which are respectively insertable into the tissue or into each organ from an open end thereof such that the two fingers have the adjoining walls of adjacent organs therebetween.
One of the fingers includes a cartridge carrying a plurality of fasteners, typically staples, arranged in at least two lateral rows while the other finger includes an anvil for curling the staple's legs into a "B-shape" upon being driven against the anvil. The stapling operation is effected by a pusher device which travels longitudinally along the cartridge carrying finger extending into one organ. The pusher mechanism acts simultaneously upon the staples at corresponding longitudinal positions in each lateral row, but successively acts upon the staples along the rows. For example, if two lateral rows of staples are provided, each row comprising twenty staples, the pusher means acts upon two staples at a time, one in each row, and successively acts upon each succeeding pair of staples.
Immediately behind the pusher means and laterally positioned between the staple rows is a knife which severs the tissue of the two organs to thereby longitudinally open the two organs to each other between the rows of staples.
up to the present, these devices were limited to severing tissue by means of a knife having a linear cutting blade. For example, the apparatus disclosed in U.S. Pat. No. 5,040,715, hereby incorporated by reference, includes a knife having a linear cutting edge surface. Further examples of such instruments are disclosed in commonly assigned U.S. Pat. Nos. 5,156,614, 5,156,315, 5,014,899, 4,520,817, 4,508,253, and 4,349,028. The disclosures of these six last mentioned patents are additionally incorporated herein by reference.
Occasionally, when tough or resilient tissue, such as ligament and/or tendon, comes into contact with known linear cutting edges, the tissue may only be partially severed. Specifically, as the linear cutting edge encounters the tough tissue, the application of cutting force against the tissue may produce an upward or lifting force on the tissue. As the cutting edge severs the tissue, the geometry of the cutting edge may permit the upper portion of the tissue to "ride up" the cutting edge and into contact with the upper finger of the apparatus. The upper finger of the apparatus may flex a sufficient amount under the force of the knife severing tissue to permit a thin layer of uncut tissue to slide therebetween. This uncut layer of tissue is referred to as a wisp. The knife, synchronized with the stapling operation so as to act only in conjunction therewith, cannot be reapplied to the wisp independent of an additional stapling operation. The remaining wisp necessitates a subsequent introduction of instrumentation to completely sever the tissue.
A need in the art therefore exists for a surgical fastening apparatus having a knife which minimizes the wisping of tissue during the severing operation. There is also a need in the art for surgical fastening apparatus capable of severing selected tough or resilient body tissue. Such surgical fastening apparatus would facilitate the severing of body tissue in adjoining operations via either open surgical procedures or endoscopic and laparascopic procedures by providing means for completely severing selected body tissue in a single actuation of instrumentation, thereby eliminating a need for subsequent introduction of instrumentation into the body.